1. Field of the Invention
The present invention relates to lens barrels and cameras provided with the same, with which a maximum aperture diameter of light-blocking members can be switched depending on the zoom position. More specifically, the present invention relates to lens barrels and cameras in which the aperture diameter of an aperture portion formed by a plurality of light-blocking members can be changed by obstructing an opening motion of the light-blocking members.
2. Description of Related Art
Aperture stops of conventional light-amount adjusting devices are realized by aperture stop mechanisms made of a plurality of iris blades, or by shutter blades also acting as the aperture stop. With the recent trend towards smaller cameras, almost all lens shutter cameras use shutter blades that also serve as the aperture stop.
On the other hand, in cameras having lens systems with a large zoom ratio, the aperture diameter varies in accordance with the focal length, so that when image-taking is performed with a predetermined aperture diameter, it is necessary to control the opening amount of the shutter blades. For this, the following mechanisms for restricting the opening amount of the shutter blades are known from the related art.
In the zoom lens disclosed in Japanese Patent Laid-Open No. 2000-352657, a mechanism is disclosed, in which a cam member of a rectilinear motion tube rotates a regulation lever inside a shutter block around an axis that is parallel to the optical axis, and the maximum aperture diameter of the shutter blades is restricted by letting the shutter blades abut against this regulation lever.
In the shutter device disclosed in Japanese Patent Laid-Open No. 2001-42384, a regulation member that can rotate around an axis parallel to the optical axis is urged into one direction by a spring, and the aperture stop diameter is switched by controlling the torque of the drive motor for rotating the shutter blades. That is to say, when the torque is greater than the spring force of the spring, then the aperture stop diameter is completely open, and when the torque is less than the spring force of the spring, then the shutter blades abut against the regulation member and are stopped, so that the aperture stop diameter is small.
Furthermore, the shutter device in Japanese Patent Laid-Open No. H09(1997)-311364 discloses a mechanism stopping the rotation of a shutter actuator midway by electric control, and restricting the maximum aperture diameter of the shutter blades.
However, in these examples of related art, components dedicated to the purpose of stopping the drive of the shutter blades midway become necessary, which makes the shutter device and the camera larger and also increases the manufacturing costs. Moreover, in Japanese Patent Laid-Open No. 2000-352657, the member (regulation lever) for, stopping the drive of the shutter blades midway is controlled with a small rotation angle around an axis parallel to the optical axis, so that it is difficult to switch the aperture diameter for each of a plurality of zoom positions, and to increase the precision of the aperture diameter of the shutter blades.
Furthermore, in configurations in which the rotation angle of the actuator driving the shutter blades is directly controlled electrically, as in Japanese Patent Laid-Open No. 1997-311364, the precision of the aperture diameter of the shutter blades becomes poorer than in cases in which the opening motion of the shutter blades is controlled mechanically.
A lens apparatus in accordance with the present invention includes a lens unit that can be moved in a direction of an optical axis, a light-blocking unit having a plurality of light-blocking members forming an aperture portion through which light passes, and a body structural member constituting a portion of a main body of the lens apparatus, wherein the light-blocking unit and the body structural member are moved relative to one another in the direction of the optical axis in accordance with a movement of the lens unit, and wherein an aperture diameter of the aperture portion is switched by moving the body structural member between a first position in which the light-blocking members are prevented from opening beyond a predetermined aperture diameter, and a second position in which the light-blocking members are allowed to open beyond the predetermined aperture diameter.
That is to say, by midway preventing or allowing an opening motion of a light-blocking member using an already available body structural member constituting a portion of the lens apparatus, the aperture diameter of the light-blocking member can be switched without utilizing a member dedicated to this purpose as in the related art, so that the lens apparatus and the camera can be prevented from becoming larger and more costly.
It is possible to adopt a configuration in which at least one of the plurality of light-blocking members includes a protrusion that protrudes out of the light-blocking unit when that light-blocking member is opened beyond the predetermined aperture diameter and that when the body structural member is in the first position, the light-blocking members are prevented from opening beyond the predetermined aperture diameter by the body structural member abutting against the protrusion.
It is also possible to adopt a configuration in which the light-blocking unit includes a first light-blocking member having a first protrusion extending in a direction perpendicular to the optical axis, and a second light-blocking member having a second protrusion that is longer than the first protrusion in the direction perpendicular to the optical axis, and that the body structural member includes a first contact portion which extends in the direction of the optical axis and which is abutted by the first protrusion when the body structural member is in the first position, and a second contact portion, which is shorter in the direction of the optical axis than the first contact portion and which can be abutted by the second protrusion when the body structural member is in the second position.
With this configuration, by changing the relative position of the light-blocking unit and the body structural member on the optical axis, it is possible not only to obstruct the opening motion of the light-blocking member by letting the first protrusion abut against the first contact portion or abutting the second protrusion against the second contact portion, but also to allow the motion of the light-blocking member. Thus, it is possible to change the aperture diameter of the aperture portion of the light-blocking member at each of a plurality of zoom positions, for example.
On the other hand, it is also possible to adopt a configuration in which the body structural member includes a first contact portion and a second contact portion, which extend in the direction of the optical axis and which is abutted by different light-blocking members of the plurality of light-blocking members, respectively when the body structural member is in the first position, and the second contact portion is longer in the direction of the optical axis than the first contact portion, and is disposed further away from the optical axis than the first contact portion at a region at the front of the second contact portion.
With this configuration, by changing the relative position of the light-blocking unit and the body structural member on the optical axis, it is possible to let the light-blocking member abut against the first contact portion or against the front region of the second contact portion. And by letting the light-blocking member abut against portions whose distances from the optical axis vary, it is possible to change the aperture diameter of the aperture portion for each of a plurality of zoom positions.
The body structural member may have a substantially cylindrical shape, and, if the tip of the protrusion has a curved surface, then the curvature radius at that tip of the protrusion is smaller than the curvature radius of the body structural member. Thus, point contact is established when the protrusion abuts against the body structural member, and the stop position of the light-blocking member is fixed at a predetermined position, so that the precision of the aperture diameter of the aperture portion can be increased.
Furthermore, by providing a front end portion of the body structural member, with a slanted surface that faces the optical axis, the light-blocking member is guided by that slanted surface towards a closing direction when it is in the open state and collides with the body structural member. Thus, the body structural member does not exert an excessive load on the light-blocking member when the body structural member and the light-blocking member collide.
Furthermore, it is possible that a plurality of reflection suppressing projections that suppress reflection of light toward an image plane side are formed in an inner circumferential surface of the body structural member, and that the reflection suppressing projections that are formed in regions of the inner circumferential surface of the body structural member against which the light-blocking members abut extend in a direction that obliquely intersects with in which the light-blocking members move. Thus, when the light-blocking members are opened and abut against the body structural member, the tips of the light-blocking members will not get caught in the recesses between the reflection suppressing projections, so that the open-close motion of the shutter blades can be carried out smoothly.
Furthermore, a body structural member may be used that guides the light-blocking unit in the direction of the optical axis. Moreover, the above-described lens apparatus of the present invention may be included in a camera.
A camera in accordance with the present invention may include a control circuit that controls the drive of an illumination unit that irradiates illumination light onto an object, and having a first object distance region and a second object distance region at a predetermined zoom position, wherein the lens apparatus can switch the aperture diameter of the aperture portion in a first object distance region to the smaller aperture diameter in a second object distance region by changing a relative position between the light-blocking unit and the body structural member, and wherein the control circuit lets the illumination unit irradiate the illumination light when an image is taken at the second object distance region.
Thus, when performing image-taking on a close range side (second focus object distance region) in a wide-angle state, the aperture diameter of the aperture portion can be made small, and by emitting light from the illumination unit, photographic imaging with little fuzziness and camera shake becomes possible.
These and further objects and features of the invention will become apparent from the following detailed description of preferred embodiments thereof taken in conjunction with the accompanying drawings.